Chapter 44 Regulating the Internal Environment

Homeostasis: regulation of internal environment Thermoregulation internal temperature Osmoregulation solute and water balance Excretion nitrogen containing waste

Regulation of body temperature Thermoregulation 4 physical processes: Conduction: transfer of heat between molecules of body and environment Convection: transfer of heat as water/air move across body surface Radiation: transfer of heat produced by organisms Evaporation: loss of heat from liquid to gas Sources of body heat: Ectothermic: determined by environment Endothermic: high metabolic rate generates high body heat

Regulation during environmental extremes Torpor: physiological state of low activity; decrease in metabolic rate 1- Hibernation: long term or winter torpor (winter cold and food scarcity); bears, squirrels 2- Estivation: short term or summer torpor (high temperatures and water scarcity); fish, amphibians, reptiles Both often triggered by length of daylight

Water balance and waste disposal Osmoregulation: management of the body’s water content and solute composition Nitrogenous wastes: breakdown products of proteins and nucleic acids; ammonia-very toxic Ammonia: most aquatic animals, many fish Urea: mammals, most amphibians, sharks, bony fish (in liver; combo of NH 3 and CO 2 ) Uric acid: birds, insects, many reptiles, land snails

Very Toxic, need access to lots of water to keep concentration low Low toxicity, so lots of water is not needed, Liver combines amonia with CO2 Disadvantage, energy is needed Low toxicity, insoluble in water, semi- solid so little water loss, more energy needed

Osmoregulators Osmoconformer: no active adjustment of internal osmolarity (marine animals); isoosmotic to environment Osmoregulator: adjust internal osmolarity (freshwater, marine, terrestrial) Freshwater fishes (hyperosmotic)- gains water, loses; excretes large amounts of urine salt vs. marine fishes (hypoosmotic)- loses water, gains salt; drinks large amount of saltwater

Takes in salt with the water, needs to keep the water and get rid of the salt, keep the water, result less urine

Takes in fresh water and ions, needs to keep the ions and get rid of excess, result lots of urine

Excretory Systems Production of urine by 2 steps: Filtration (nonselective) Reabsorption (secretion of solutes) Protonephridia: flatworms (“flame-bulb” systems) Metanephridia: annelids (ciliated funnel system) Malpighian tubules: insects (tubes in digestive tract) Kidneys: vertebrates

Flatworm: Phylum Platyhelminthes Dead-end tube Draws water and solutes in from the interstitial fluid, filters it, moves urine outward through the tubule, exits through openings

Earthworm: Annelids Metanephridium: excretory and osmoregulatory

Insects and other terrestrial Arthropods Immersed in hemolymph: (circulatory fluid) Key adaptation that contributed to the success of these animals on land

Kidney Functional Units Renal artery/vein: kidney blood flow Ureter: urine excretory duct Urinary bladder: urine storage Urethra: urine elimination tube Renal cortex (outer region) Renal medulla (inner region) Nephron: functional unit of kidney Cortical nephrons (cortex; 80%) Juxtamedullary nephrons (medulla; 20%)

Nephron Structure Afferent arteriole: supplies blood to nephron from renal artery Glomerulus: ball of capillaries Efferent arteriole: blood from glomerulus Bowman’s capsule: surrounds glomerulus Proximal tubule: secretion & reabsorption Peritubular capillaries: from efferent arteriole; surround proximal & distal tubules Loop of Henle: water & salt balance Distal tubule: secretion & reabsorption Collecting duct: carries filtrate to renal pelvis

Basic Nephron Function

Nephron Function, I Proximal tubule: secretion and reabsorption

Nephron Function, II Loop of Henle: reabsorption of water and salt Distal tubule: secretion and reabsorption

Nephron Function, III Collecting duct: reabsorbs water, salt, some urea

Kidney regulation: hormones Antidiuretic hormone (ADH) ~ secretion increases permeability of distal tubules and collecting ducts to water (H2O back to body); inhibited by alcohol and coffee Juxtaglomerular apparatus (JGA) ~ reduced salt intake--->enzyme renin initiates conversion of angiotension (plasma protein) to angiotension II (peptide); increase blood pressure and blood volume by constricting capillaries Angiotension II also stimulates adrenal glands to secrete aldosterone; acts on distal tubules to reabsorb more sodium, thereby increasing blood pressure (renin- angiotension-aldosterone system; RAAS) Atrial natriuretic factor (ANF) ~ walls of atria; inhibits release of renin, salt reabsorption, and aldosterone release